Pressure correction to a mineral reaction ($\Delta G_{\mathrm{solids}}={\int }_{P_0}^P\Delta V_{\mathrm{solids}}dP$)

At fixed temperature, $dG=VdP$ gives the pressure correction for the participating solids. Constant reaction volume reduces the integral to $\Delta V_{\mathrm{solids}}(P-P_0)$. A gas product treated by chemical fugacity instead contributes $\nu RT\ln (f/P_0)$ relative to its reference state. Adding a separate gas-volume correction to that term would double count the same pressure dependence.